The incidence of the neuropathological lesions and the severity of the clinical symptoms in multiple sclerosis (MS) are correlated with the amount of the transferred autoreactive T cells. The balance between the T helper 1 (Th1) and T helper 2 (Th2) cytokine phenotypes may affect the activity of the disease in MS patients. Interleukin‐10 (IL‐10) is a cytokine secreted by Th2 cells. Thus, it has been thought that inducing IL‐10 may have therapeutic effects in the treatment of MS patients. In this study, in order determine whether different types of prophylaxis change the secretion of IL‐10, we measured the levels of IL‐10 in relapsing‐remitting type multiple sclerosis (RRMS) patients receiving interferon‐β 1b (IFN‐β 1b) or azathioprine (AZA). Our study consisted of RRMS patients (n = 45) and healthy subjects (n = 15) as control group. Patients were categorized into three groups as those receiving either IFN‐β 1b or AZA and those not receiving prophylaxis. Each group was compared with the control group. Serum IL‐10 levels were determined using ELISA method. IL‐10 levels of those receiving IFN‐β 1b were found to be significantly higher than that of other groups. These results support that the ability of inducing anti‐inflammatory cytokine IL‐10 plays a role in the clinical advantage of IFN‐β 1b in MS treatment.